1. Field of the Invention
The present invention relates to a starter for cranking an internal combustion engine, the starter having a mechanism for establishing engagement of a pinion gear with a ring gear of the engine by restricting rotation of the pinion gear.
2. Description of Related Art
An example of this type of starter is disclosed in JP-A-9-42123. A portion of this starter is illustrated in FIG. 11 attached hereto. A pinion gear unit 100 composed of a pinion gear 110, a rotation-restricting ring 120 having depressions 121 on the outer periphery thereof and a thrust bearing 130 is coupled to an output shaft 150 of the starter by means of a helical spline. Rotation of the pinion gear unit 100 is restricted by engaging an engaging portion 140 of a pinion-rotation-restricting member with the depressions 121, while the output shaft 150 is slowly driven by an electric motor. The pinion rear unit 100 helical-spline-coupled to the output shaft 150 is pushed forward toward the ring gear, thereby establishing engagement between the pinion gear 110 and the ring gear. Then, the restriction of rotation of the pinion gear unit 100 is released, and the output shaft 150 is rotated at a full speed to crank up the engine. After the engine is started, the pinion gear unit 100 is returned to its original position.
In the starter briefly described above, since the pinion gear 110 and the rotation-restricting ring 120 are integrally formed, the die for forging the integral body becomes complicated, and accordingly its manufacturing costs become high. Further, in case the outer diameter of the pinion gear 110 is larger than the outer diameter of the rotation-restricting ring 120, a high level forging technology will be required.